Gravity separators are used in various industries. Gravity tables are generally used for separating dry particles of similar, or identical, size and shape, but which vary in specific gravity and/or weight. For example, in the seed industry, low germination seed generally is lower density than seed with desired germination characteristics. Thus, the light seed is separated and discarded while the heavy seed goes on to be used. A middlings fraction (weight in between the light and heavy seed) is usually rerun for better separation and then discarded.
The grains or particles of product are fed continuously onto the separating deck surface of a gravity separator providing a bed of material over the surface. The bed is fluidized by a uniform pressurized air system, thereby stratifying the light material to the top of the product bed and allowing the heavy material to contact the deck surface. The deck is inclined from side to side and from inlet end to discharge end at adjustable angles. The deck is moved at low amplitude and high frequency up hill. The heavy material contacting the wire mesh deck surface moves up, while the light material fluidized by the air system moves down due to gravity. Flaps, or discharge gates, direct the weight fractions off the appropriate edge of the table.
Conventional wisdom in gravity tables is to utilize the movement of the deck and air pressure to start moving light product up while allowing they heavy product to contact the deck and begin its movement to the high side of the table. Because the depth of the product in the feed zone is much deeper due to the smaller area of the deck and there is an initial lack of movement of the product, it is difficult to effectively stratify the product in this crowded area. This crowding significantly reduces the throughput capacity of the machine and can reduce the separating efficiency. Attempts at better distribution of product have been made using various levels of airflow, pitch and slope, screen designs deck configurations, and the like, however, these design changes have only resulted in minimal increases in separation efficiency. Therefore, there is a need for an improved gravity table which achieves increased efficiency.
An object of the invention is to provide gravity separators with more efficient separation.
Another object of the invention is to provide a method for improving efficiency of gravity separation.
These and other objects, features, and advantages will become apparent after review of the following description and claims of the invention which follow.
The present invention greatly improves the separation efficiency of gravity tables. The invention has xe2x80x9cpinsxe2x80x9d in the inlet area of the gravity table deck. The pins xe2x80x9csplitxe2x80x9d the separation force into two directions and creates space within the product bed making movement within the bed easier. Additionally, the invention has a change of the shape of the light rail wall of the deck. The deck shape has been reconfigured by bringing the light rail side wall of the deck toward the middle of the table changing the flow pattern of the product fractions across the deck.